<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <script type="text/javascript">
            function timedMsg() {
                var t = setTimeout("alert('5 秒！')", 5000);
            }
        </script>
    </head>
    <body>
        <form>
            <input type="button" value="显示定时的警告框" onClick = "timedMsg()">
        </form>
        <p>请点击上面的按钮。警告框会在 5 秒后显示。</p>
    </body>
</html>